“We must make sure that the biggest providers are not able to limit broad participation in the spectrum auction,” said Roger C. Sherman, FCC wireless telecommunications bureau chief.

So the FCC now is asking for comment on a proposed rule that would ban joint bidding of the sort planned by Sprint and T-Mobile US for former TV broadcasting spectrum in the “incentive auction” for that spectrum.

The FCC “tentatively concludes that joint bidding arrangements between nationwide providers should not be allowed,” Sherman said.

Foreign ownership restrictions would not be an issue, since Deutsche Telekom already owns most of T-Mobile US. Trading a French majority owner for a German majority owner should not prove troublesome.

A purchase by Iliad also would preserve the current market structure of four leading national providers, something regulators and antitrust authorities have said they prefer.

T-Mobile US would seem to gain, either way. T-Mobile US would receive a breakup fee of possibly $2 billion in the event a Sprint acquisition bid was rejected. T-Mobile US at present is the fastest-growing of the four major U.S, mobile carriers, and almost certainly will pass Sprint for the first time and become the number-three provider in terms of subscriber share.

Long term, an independent T-Mobile US would still need to amass more scale to compete long term with AT&T and Verizon, and organic growth is unlikely to provide sufficient mass, soon enough.

But some might argue, with good reason, that the longer T-Mobile US waits, the higher its value grows.

In other words, T-Mobile US can wait. Dish Network already has said it could bid for T-Mobile US if the Sprint deal should be blocked. And Iliad’s surprise bid could trigger more thinking by other potential acquirers.

Iliad, for its part, is not likely done, though it almost certainly has to line up additional support for a new bid.

Whither Sprint?
That might not be true for Sprint. The strategy some expected a SoftBank-owned Sprint to take already has been usurped by T-Mobile US. Should Sprint fail to acquire T-Mobile US, it is not so clear what Sprint can do to create a stronger role in the market, based solely on organic growth.

Given enough time, Sprint would be the target, not the acquirer. In fact, one might already argue that SoftBank’s original vision for buying Sprint has proven to be a mistake.

T-Mobile US argues it does not need to be acquired by Sprint, and has other growth options. What is Sprint’s plan, in the event a deal is nixed?